Science & Society

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PUZZLE PLANT After bursting on the scene in the 1960s, marijuana remains a substance with uncertain effects on mental health and medical conditions.

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EMBRYO, INTERRUPTED A 5-day-old human embryo is usually composed of about 200 cells in a hollow ball configuration called a blastocyst (left). Embryos edited to remove the OCT4 gene (right) fail to make normal blastocysts.

K. Niakan/Nature 2017

MICROBE BREWS Scientists are looking for a few good yeasts to enhance beer brewing. Each flask (above) contains the same liquid ingredients and a different kind of yeast.